Electric circuit breaker



tow-neg.

' Inventor- Robert T. Case y His R T CASEY ELECTRIC CIRCUIT BREAKERFiled Aug. 11, 1948 Oct. 30, 1951 Patented Oct. 30, 1951 ELECTRICCIRCUIT BREAKER Robert '1. Casey, Bristol, Conan, assignor, by memoassignments, to General Electric Company, a

corporation of New York Application August 11, 1948, Serial No. 43,585

My invention relates to electric switches commonly called circuitbreakers oi the type which automatically opens the circuit upon acontinued slight overload or upon a sudden heavy overload and which canbeF operated to open or close a circuit manually or to reset it manuallyin case of an automaticopening in the circuit.

The principal object is to greatly simplify the automatic protectivemechanism and to provide a magnetic release that can be readily added toa conventional thermal release mechanism and thus convert it to acombination trip device.

It will be seen that the invention relates principally to the automaticrelease mechanism in which a magnetic release device is mounted on thethermal release device and thus forms a comhination applicable to manycircuit breaker switching mechanisms.

Fig. l is a side view and section showing a conventional switch in acasing and embodying my thermal and magnetic circuit breaking devices,the parts being shown in the circuit closed position.

Fig. 2 is an enlarged fragmentary side and partially sectional viewshowing the effect of the thermal release action, the armature beingshown in its position at the instant of release of the breaker action.

Fig. 3 is a view of the same parts as those in Fig. 2 but with thearmature in the position at the instant of tripping due to magneticrelease.

Fig. 4 is a fragmentary view showing the magnetic release member and theend of the thermal member looked at from the right of Figs. 2 and 3.

Fig. 5 is a plan view of the parts of Fig. 4 but showing the thermalstrip in section.

Fig. 6 is a fragmentary sectional view of the release parts in theposition they occupy after complete release of the breaker.

The switch mechanism per se 1 may be of any suitable type having aspring pressed trip arm a releasable to cause automatic opening and maybe mounted in a casing 9 with a cover 9' of suitable construction.

The stationary contact IU of the switch is connected to the circuitterminal H and the movable contact I2 is flexibly connected to the footof the thermal strip IS. The outer end of the strip 13 is flexiblyconnected to the circuit terminal H in any suitable manner. v

Near its outer end the strip [3 carries a catch II with which the tip ofthe trip arm 8 normally engages. When the catch is retracted from thetrip arm, the arm flies upward as indicated in Figs. 2 and 3 and thecircuit is broken in the usual manner.

7 Claims. (01. 200-88) This catch II is connected to a part of thearmature it of the magnet I1. The flanges ot the magnet embrace theedges of the strip I! which supports the magnet and its armature. Forthis purpose, a non-magnetic headed stud 18 passes through the magnetand its armature and is screwed into the non-magnetic bimetal strip 13and held by the nut l9 screwed onto the threaded end of the stud l8 sothat the action of the catch may be adjusted. A spring 20 on the stud isinterposed between the strip I3 and.

the armature and presses the armature toward the head of the stud asshown in Figs. 1 and 2. The boss 21 projecting from the strip i3 servesto space the upper edge of the armature away from the magnet and thespring biases the armature and its catch away from the magnet, the tripmember being biased to the open circuit position tilts the armatureagainst the boss 2!.

When the bimetal strip 13 is heated by prolonged moderate overload, itis warped as shown in Fig. 2 and thus releases the breaker trip arm fromthe catch.

In case of a sudden heavy overload passing through the strip IS, themagnet i1 is energized and draws the armature 16 into the position ofFig. 3 and releases the trip arm. To assist in positioning the magnetand its armature, I may v provide a non-magnetic guide 22 which embracesthe edges of the magnet and its armature.

It will be seen that such a combination of thermal and magnetic devicesis extremely simple and readily installed. The magnet and its armatureand the catch and guide are all secured in place on the bimetal strip bya single screw.

By reason of the fact that the magnet and its armature and catch aremounted upon and movable with the bimetal member, the air gap betweenthe magnet and armature remain constant as the bimetal member starts towarp so that the characteristic sudden overload point is not changed bythe incomplete" slow warping movement as caused by a slow moderateoverload.

It will also be seen that the catch for the magnetic release is exposedwhen the cover of the housing or casing is removed so that it is readilyaccessible for assembly and for inspection and adjustment.

I claim:

1. Automatic release mechanism for a circuit breaker including a tripmember, a bimetal strip anchored at one end and movable at the other endwhen overheated, a magnet embracing at least one surface of the strip,an armature coacting with the magnet, a headed screw stud passingthrough the armature, strip and magnet, a spring I on said stud betweenthe strip and the armature and a catch'carried by said armature andcoacting with said trip member.

2. Automatic release mechanism for a circuit breaker comprising abimetal strip anchored at mally movable strip member, a magnet carriedby and movable with said strip member upon an overload in the circuit, astud carried by said magnet and said strip member and movable therewith,said stud having a head spaced from said strip member, an armaturemounted to tilt on said stud between said strip member and said head,said strip member having an abutment for one edge oi! said armature atone side of said stud, said armature having a catch shoulder for holdingthe trip arm under normal circuit conditions and a spring on said studbetween said strip member and said armature, said armature being movableindependently .of said strip member upon a sudden overload in thecircuit.

4. Release mechanism as set forth in claim 3 in which the stud isadjustable through said magnet to modify the action of the armature.

5. In a circuit breaker having contact mechanism with a spring biasedactuator, current actuated latching mechanism including a thermallywarpable strip fixed at one end and movable at the other end, a magnetat the movable end of said strip, a stud passing through said strip andsaid magnet and having a head spaced from said strip, an armaturemounted on said stud between said head and said strip, said strip havinga boss projecting toward one edge of said armature at one side of saidstud, said armature having a shoulder at the opposite side of said studfor holding the actuator of the circuit breaker and a spring compressedbetween said strip and said armature biasing said armature toward saidhead.

6. Automatic release mechanism for a circuit breaker havingaspring-pressed trip arm, a current actuated magnet having an armature, a

, 4 I w bimetal support therefor, a stud carried by said magnet andsupport and having a head spaced irom said magnet, an abutment for oneedge of said armature between said magnet and said armature, thearmature being mounted on said stud to tilt at one edge on said abutmentbetween said head and said magnet, a catch shoulder carried by anopposite edge of the armature for, holding the trip arm under normalcircuit conditions and a spring between said magnet and said armatureior pressing said armature away from said magnet and against said headwhen the magnet is energized and the trip arm is released, said studbeing adjustable through said support.

7. A circuit breaker including relatively movable contacts, a releasablemember operable when released to effect opening of said contacts, tripmeans including a bimetal element electrically connected to be traversedby current, electroresponsive means comprising a pair of magneticmembers on opposite sides of said bimetal element and energized by thecurrent flow therethrough, both of said magnetic members being movable,one of said magnetic members being movable magnetically relative to theother to efl'ect release of said releasable member upon the occurrenceof a heavy overload and the other magnetic member being movable uponbending of said bimetal element to efiect release of said releasablemember upon the occurrence of a smaller overload and a single screw studadjust-= able in said bimetal element and supporting both of themagnetic members.

ROBERT T. CASEY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

